A power circuit breaker or circuit interrupter can be divided into three major components: arc-interrupting and current-carrying contacts; entrance bushings; and an operating mechanism. Each of these components is vital to the operation of a circuit breaker; weakness in any one will result in unsuccessful breaker operation. After a circuit breaker has been placed in service, practical experience has shown that the operating mechanism requires the most attention.
The function of the operating mechanism is to open and close the breaker contacts. This, by itself, is a comparatively simple task. However, circuit breaker operating mechanisms are usually specified to meet at least the following design criteria: 1) allow contacts to open and then reclose once in a total maximum time of three to five 60 hz electrical cycles (0.05 to 0.08 seconds); and 2) perform at least five closing and opening operations without the energization of a prime mover.
Conventional spring loaded operating mechanisms for operating high voltage power circuit breakers, commonly known as a “stored energy mechanism,” tend to use an electric motor to recharge the closing spring after each closing operation. An example of a conventional electric motor recharging spring loaded operating mechanism is depicted in FIG. 1. The arrangement of the mechanism drive linkage enables the closing spring to also charge the opening spring as part of the closing sequence. Without electric power and, thus without the availability of the electric recharging motor, these conventional operating mechanisms tend to limit breaker operation to an Open-Close-Open (O-C-O) cycle. This raises concerns surrounding conditions during loss of electricity. In the event that the electric motor is available for recharging the spring, such recharging time is specified to be 15 seconds, which results in the breaker operation being limited to an Open-Close-Open-15 second recharge-Close (O-C-O-15 sec-C).
Hydraulic storage systems have been explored for designs requiring breakers with 4 or 5 operations under conditions where power has been lost, or electricity is unavailable. A hydraulic accumulator is used to recharge the closing spring mechanism. By varying the size of the hydraulic accumulator, the desired number of stored operations can be achieved.
Attempts to meet the requirement of multiple operations using storage batteries or stand-by generators have been unsuccessful or operationally unacceptable.
It is within the aforementioned context that a need for improved spring mechanisms for operating high voltage power circuit breakers has arisen. Thus, there is a need to address one or more of the foregoing disadvantages of conventional systems and methods, and the embodiments presented herein meet this need.